A standard belt press has a frame having horizontally extending and vertically spaced upper and lower plates defining a horizontally extending gap having an upstream end and a downstream end, vertically spaced upper and lower upstream drums rotatable about respective horizontal axes at the upstream end, vertically spaced upper and lower downstream drums rotatable about respective horizontal axes ad the downstream end, and upper and lower endless belts spanned over the respective upper and lower drums and each having a working stretch lying between the plates and a return stretch. Upper and lower sets of rollers engaged between the working stretches and the respective plates can be recirculated as the belts are advanced to move the working stretches horizontally in a transport direction to displace a workpiece in the direction through the gap so that the working stretches are supported on the respective plates by these rollers.
As described in German patent document 2,643,346 the drums are pivotal about vertical axes that centrally intersect their rotation axes. Thus these drums can swing limitedly with their axes moving in horizontal planes. The disadvantage of this is that as the drums are moved to adjust the belts on center they have a deleterious effect on the tension in the belt, which in turn affects how the rollers move. This is particularly the case when the rollers are not constrained or guided, that is when they can move fairly freely at some spacing from one another and when they have a length which is equal to the width of the belts. In particular when the belts are very long, it is hard to keep them aligned in such a press.